I thought I'd share a fun little trick that I discovered when I was trying out all different sorts of variations for our Foaming Treasure Stars. I discovered a neat thing that makes HUGE foaming reactions and is really quick and easy. This is what we do every time now because it is just too fun!

To demonstrate the differences between different approaches, my trusty co-scientist and I set out to run some tests. We know that when you're conducting a scientific investigation, you keep all but one thing the same. So we used the same amount of green baking soda each time, added it to the same little glass bowl, placed that inside the same glass pie dish, and reacted it with the same amount of vinegar each time. Since S is only 5, I didn't worry about gathering hard data - we decided to just use our eyes (and these photos) to talk about what we discovered.

So first up, we did baking soda + vinegar. As you can see, it foamed up out of the small bowl and filled about half of the pie pan. The foam dissipated very quickly and there were only a few sparse bubbles about one minute afterward.

Next we tried baking soda + one squirt of dish soap (AKA washing up liquid) on top and reacted it with the same amount of vinegar as above. This time we had way more foam. It reached the top of the pie pan. And after about 1 minute there were still quite a few bubbles left.

Next we tried baking soda + one squirt of dish soap mixed in, such that the soap evenly coated all the baking soda. Then we added the same amount of vinegar. Much to S's delight this one just barely spilled over the edge of the pie pan. There were more bubbles left over after 1 minute than there were with our previous attempt.

Finally we tried baking soda + vinegar with one squirt of dish soap added to it. I gave the vinegar two gentle swishes to mix the dish soap just a little. This reaction was HUGE. It was even bigger than the middle photo but I had to grab some paper towels, hahaha. It easily spilled out on to the table and at a minute post-reaction there were still quite a few bubbles - a tiny bit more than the previous attempt.

Conclusion? The best and foamiest baking soda and vinegar eruptions are made by reacting baking soda with vinegar that has a few drops (AKA one squirt) of soap mixed into it.

Of course we needed to demonstrate the best version with a rainbow. Soooo pretty, right? To make our rainbow eruptions, we mixed baking soda with different shade of liquid watercolors (once you add a few squirts, mix well with a spoon or your hands until the color is evenly dispersed). You can either air-dry the colored baking soda, or you can use it while it is still damp (dried works slightly better). If you don't have liquid watercolors, you can add several drops (5-15) of food coloring to a teaspoon of water. Add more water as needed to disperse the color.

How does it work? When baking soda and vinegar mix, they release carbon dioxide (this is the same gas that is in the bubbles in your carbonated drinks). If you add soap, the carbon dioxide essentially blows bubbles in it. To get the most bubbles, you want to be sure as much of the carbon dioxide gas comes into contact with soap as possible - this is why both of the reactions where we mixed the soap in created more foam than the reaction where we just squirted soap in the middle. Because soapy baking soda tends to stick together a bit, it's slightly harder for the vinegar to reach all that baking soda, so the third version we tried was just a little less dramatic.

We hope all of your baking soda and vinegar reactions are of the dramatic foaming variety now. :)

All activities here are activities I feel are safe for my own children. As your child's parents/guardians, you will need to decide what you feel is safe for your family. I always encourage contacting your child's pediatrician for guidance if you are not sure about the safety/age appropriateness of an activity. All activities on this blog are intended to be performed with adult supervision. Appropriate and reasonable caution should be used when activities call for the use of materials that could potentially be harmful, such as scissors, or items that could present a choking risk (small items), or a drowning risk (water activities), and with introducing a new food/ingredient to a child (allergies). Observe caution and safety at all times. The author and blog disclaim liability for any damage, mishap, or injury that may occur from engaging in any of these activities on this blog.

I totally forgot to include that! EEK! Thank you for the reminder - adding it to the post now. I added liquid watercolors and mixed well. I allowed it to completely dry before we did the experiment (because we were away on vacation), but it will also work when it is damp. Hope that helps!

Fantastic! And yikes I totally forgot to include that in the post! Thank you for the reminder - adding it now. :) We used liquid watercolors - if you have food coloring, be sure to add it to water first (about 1 teaspoon and 10-15 drops) before mixing it in. The water should help disperse the coloring. Hope that helps! :)

Hey! I forgot to tell you that I followed your advice: wonderful result, the girls were excited, and the colours were great. Thanks again! Good luck for your book. Any chance to get a signed version? ;-)CheersPascal

This is a great way to talk about the algebraic property of Associativity. Use B, S and V for baking soda, soap and vinegar. When you did (B+S)+V it was different than when you did B+(S+V). Your little one will totally be able to get the idea with just those two expressions. When you ask her to repeat the words, "This means it is NOT associative," you'll be embedding some important math vocabulary as well as promoting a positive math attitude!

I love the addition of color for a fun study. Great way to mix Science and Color recognition. I would love it if you linked up at the Geeky Educational LInk Up! http://www.morethanacouponqueen.com/search/label/Geeky%20Educational%20Link%20Up

This was fun! Just want to remind people that those with sensitive skin, eczema, etc. can have a bad reaction to touching this for even a minute. Baking soda is strong, and my poor girl burned herself (not badly) before we thought to wear gloves. I wish I thought of this before starting!

Ummmm sorry but couldyou tell ushow much you used as I used 1/2 a cup of vinegar for every 3 table spoons of baking soda but I didnt know how much dishsoap to add and it wasn't looking as well as yours

I'm working on a STEM night and thinking making this as a station would be fun, but I think it would be helpful to have the vinegar/soap solution made up beforehand for volunteers. Would you have any more specific measurements or ratio for larger volumes of vinegar and soap?